Sulphate transporter gene mutations in apparently isolated club foot

Editor—Diastrophic dysplasia was originally ascribed to sulphate transporter gene ( DTDST ) mutations. The DTDST gene is now also known to account for a variety of bone dysplasias including diastrophic dysplasia, atelosteogenesis type II (AO2), and achondrogenesis Ib.1-3 Abnormally sulphated cartilage proteoglycans with deficient cartilage sulphate content has been reported in these conditions,4 suggesting that a variable residual DTDST activity probably accounts for the broad spectrum of clinical phenotypes at this locus.5 While a predominant founder mutation in the splice donor site of a previously undescribed 5′ untranslated exon accounts for the disease in Finland, more than 30 mutations have been reported so far world wide6 and compound heterozygosity for variably deleterious mutations probably explains the broad spectrum of clinical phenotypes at the DTDST locus.2 7 8 The R279W mutation is the most common mutation in non-Finnish patients and, apart from its original report in an AO2 patient, compound heterozygosity for this mutation has been consistently associated with a non-lethal phenotype. Recently, Superti-Furga et al 9 reported homozygosity for the R279W mutation in an adult affected with multiple epiphyseal dysplasia, normal stature, club foot, and double layered patella. Here, we add further support to this view and report on the association of apparently isolated club foot with the homozygous R279W DTDST mutation in two unrelated sibships of western French ancestry (Brittany). In family 1, dizygotic twins, a boy …